The present invention relates to a process for bonding filament with aqueous based polyethylene terephthalate or polyurethane bonding agents via a foam delivery system.
Historically, approaches for treating filament such as sewing thread have focused on applying a compound on the surface of the filament. This has usually been achieved by applying an organic solvent solution of the compound to the filament followed by solvent evaporation. Recently, radiation has been used to activate the primed surface of the filament. However due to pressing environmental concerns and economic feasibility, it is desirable to replace those systems with an aqueous based system.
U.S. Pat. No. 5,230,922 discloses a process for the bonding of lightweight fleeces. The process involves wetting a fleece with cold water, subjecting the fleece to suction extraction to remove excess water, impregnating the wetted fleece with a liquid bonding agent, heating the fleece impregnated with the bonding agent, and winding it up. U.S. Pat. No. 5,230,922 discloses that the amount of binder applied is highly dependent on the desired end product. It neither teaches a range for the amount of bonding agent to apply nor does it suggest the use of polyurethane or polyethylene terephthalate aqueous based bonding agents. Additionally, it is directed toward lightweight fleeces, not filaments.
U.S. Pat. No. 4,847,116 discloses a method of manufacturing a composite wet press felt fabric in which a homogeneous foam of polymeric resin particles, binder material, and a solvent is deposited on the surface of the fabric. The foam is distributed on the surface of the fabric in a uniformly thick layer. Heat treatment is applied to the base fabric to evaporate the solvent in the foam, to fuse the polymeric resin particles to each other and to the base fabric, and to cure the binder material. Representative polymeric resins are polyolefins such as polyethylenes and polyurethanes. The binders can be high temperature resistant resins which are applied as liquids and which cure to a solid film under heat.
German Patent DE 4327783A1 relates to a bonded sewing thread in which bonding is achieved by impregnating the outer surface of the thread with at least one precursor material which can be activated before the thread is used. After activation, the precursor is chemically changed into a product which increases the bonding of the thread.
U.S. Pat. No. 4,141,315 relates to an apparatus for applying a thin layer of liquid systems to fibers, threads, or sheets which are moved uniformly in a linear direction. Liquid systems may be lubricants, antistatic agents, emulsifiers, wetting agents, and bactericides. They may be applied uniformly, in controllable quantities, and in the form of a foam to fibers, threads, or sheets. The fibers, threads, or sheets to be coated may be of polyamides, polyesters, polyacrilonitriles, polyolefins, carbon, glass, asbestos, or aluminum oxide. However, the process is particularly suitable for threads and fibers of polyamide-6. No reference is made to the aqueous based bonding agents of the present invention.
U.S. Pat. No. 2,533,167 relates to an apparatus and to a method of applying a liquid adhesive to a web of fibrous material. The method comprises supporting the web adjacent and above, but out of contact with, the exposed surface of a pool of liquid adhesive. Gas is forced under pressure upwardly from below the surface of the pool to form bubbles. The web is then passed through the bubbles causing them to burst and deposit their liquid adhesive on the web. The web of fibers is then heated and dried. Although U.S. Pat. No. 2,533,167 teaches the application of adhesives to fiber, it does not disclose the aqueous based bonding agents of the present invention.
xe2x80x9cCoating Carbon Fibers with Thermoplastic Polymers Using Aqueous Foamxe2x80x9d by R. R. Chary and D. E. Hirt discusses a process using aqueous foam as a carrier medium to deposit polymer on fiber tow such as carbon fibers. No reference is made to the aqueous based bonding agents of the present invention.
A process for bonding filament with aqueous based polyethylene terephthalate or polyurethane bonding agents via a foam delivery system is disclosed. The process includes the steps of: (a) providing the filament; (b) providing a foam prepared by foaming a solution comprising an agent selected from the group consisting of polyethylene terephthalate or polyurethane bonding agents; (c) applying the foam to said filament; and (d) drying and curing said filament.